The present invention relates to a novel solid phase assay device for conducting assays, especially immunochromatographic assays, for the determination of analytes in samples, and to methods of using the device.
A type of solid phase assay devices comprises a plate-shaped flow matrix of bibulous material, usually a membrane strip, such as of cellulose nitrate or glass fiber, in which liquid can be transported laterally (i.e. in the plane of the strip) by capillary forces in the membrane. The membrane usually has a sample application zone, and a a detection zone downstream of the sample application zone. In the detection zone, usually a capturing reagent for the analyte is immobilized. To conduct an assay, the application zone is contacted with the liquid sample to be assayed for the analyte of interest. The device is maintained under conditions sufficient to allow capillary action of liquid to transport the analyte of interest, if present in the sample, through the membrane strip to the detection zone where the analyte is captured. The capillary liquid flow is usually insured by an absorbing pad or the like at the downstream end of the strip. A detection reagent, usually labelled, is then added upstream of the detection zone and interacts with captured analyte in the detection zone, and the amount of captured analyte is measured. Often, the detection reagent is pre-deposited in or on the membrane strip, e.g. in the form of diffusively movable particles containing fluorophoric or chromogenic groups, either upstream of the sample application zone or between the sample application zone and the detection zone.
EP-A-306 336 discloses an assay device of the general type outlined above, wherein the strip of bibulous material is enclosed in a housing. The housing has a first opening for introducing the sample into the device, and second opening for introducing another liquid reagent than the sample into the device, such as a member of the signal producing system used. The device can also include additional means than the two openings for introducing additional assay reagents into the device, e.g. a third opening in the housing or a breakable container with liquid reagent included in the device. The device is said to permit timed reagent additions even though the operator carries out all the steps in rapid succession.
WO 99/36776 discloses an assay method of the general type described above based on the discovery that zonewise migration of desired assay liquids in a predetermined order may be obtained if the liquids are added simultaneously or almost simultaneously to adjacent zones in the strip.
Carrying out an assay with one of the devices described in the two publications mentioned above require, however, a number of steps to be taken by the operator in a short time, and especially the simultaneous addition of liquids according to the method of WO 99/36776 may be difficult or inconvenient for the operator to perform.
An object of the present invention is to provide an assay device for conducting an assay for the determination of an analyte, which device permits simultaneous initiation of flow of sample and at least one other assay liquid.
Another object of the present invention is to provide an assay device which is suitable for performing a sequential assay with a predetermined flow of sample and assay liquids through the device.
Still another object of the present invention is to provide a device which is easy to handle for the operator and requires a minimum of operation steps.
According to the present invention, the above and other objects and advantages are obtained with a test device for conducting an assay for the determination of an analyte in a sample, which device comprises (i) a housing, and within said housing, (ii) a flow matrix allowing liquid to be transported by capillary action and having at least one zone with immobilized capturing agent capable of directly or indirectly binding the analyte, (iii) a liquid container for sample liquid, and (iv) at least one liquid container for liquid other than sample liquid. The device is characterized in that it further comprises (v) separation means between the flow matrix and the liquid containers, wherein said separation means are mounted in a movable relationship with the liquid containers to in a first position prevent liquid contact of the flow matrix with the liquid containers, and in a second position permit liquid receiving contact of the flow matrix with the liquid containers.
The flow matrix is preferably plate or sheet shaped, such as a membrane strip, which allows lateral liquid flow therethrough.
The term xe2x80x9cliquid containerxe2x80x9d is to be interpreted broadly and basically encompasses any liquid holding element or means capable of receiving and delivering liquid. Thus, the liquid contaner may be a recoptacle or well with the opening facing the flow matrix, wherein the opening is closed or sealed by the above-mentioned liquid-tight element. The liquid container may also be a body capable absorbing and holding a predetermined amount of aqueous liquid, such as, for example, a pad or a sponge body. Usually, such a body is enclosed in a well or other room sealed by the liquid-tight element.
In one embodiment, the liquid containers are mounted adjacent to a face, usualy the top face, of the flow matrix, and the separation means comprise a flat liquid-tight element sandwiched between the liquid containers and the flow matrix. Preferably, this liquid-tight element is at least partially removable from the housing and may, for example, be a pull-out film.
In an alternative embodimnent, the liquid containers are mounted in a movable relationship with the flow matrix, i.e. in a position, the liquid containers are separated from the flow matrix, and may be brought to a second position where the containers are in liquid transferring contact with the flow matrix.